A worker, who declined to be identified, walks past cows as they feed at the dairy farm Sunny Dene Ranch Thursday, Dec. 25, 2003, in Mabton, Wash. The farm has been quarantined by the state because a cow that came from the farm has apparently been infected with disease. (AP Photo/Elaine Thompson)

As the American beef industry struggles with its first case of mad cow disease, the Department of Agriculture is debating whether to do far more screening of meat and change the way meat from suspect animals is used, department officials say.

The officials declined to say exactly what they would recommend, but they acknowledged that European and Japanese regulators screen millions of animals using tests that take only three hours -- fast enough to stop diseased carcasses from being cut up for food.

American inspectors have tested fewer than 30,000 of the roughly 300 million animals slaughtered in the last nine years, and they get results days or weeks later.

But the American system was never intended to keep sick animals from reaching the public's refrigerators, said Dr. Ron DeHaven, the Agriculture Department's chief veterinarian.

It is "a surveillance system, not a food-safety test," he said in an interview. Statistically, it is meant only to assure finding the disease if it exists in one in 1 million animals, and only after slaughter.

A beef industry spokesman said that cattle ranchers would endorse adopting more rapid tests.

Western European countries generally test all cattle over 2 years old, all sick cattle and a small percentage of apparently healthy ones. Last year, they tested a total of 10 million.

Japan tests all the 1.2 million cows it slaughters each year.

DeHaven said Japan tested "too much" and called it "like a doctor testing every patient who comes through the door for prostate cancer."

American beef is still "extremely safe," said Daniel L. Engeljohn, a policy analysis official in the Agriculture Department's Food Safety and Inspection Service, but the discovery of the disease "will spur the U.S. to look at the preventive measures it's had in place for the last decade."

Critics of the industry called the current testing inadequate and said they had been warning for years that mad cow disease was in American cattle but undetected because too few animals were tested.

They accused the Department of Agriculture of failing to be the vigilant guardian over the nation's dinner table and said it did not fulfill the common claim that its inspectors test all obviously sick cows.

How many "downers" -- cows too sick to walk -- are slaughtered each year is in dispute. The beef industry says it is only about 60,000 among older animals, while animal rights advocates cite figures based on European herds that suggest nearly 700,000.

The Agriculture Department says its best guess is from a 1999 beef industry survey that estimated there were 195,000 downers on ranches, feedlots and slaughterhouses that year.

In any case, only 20,526 animals were tested last year; through the 1990s, only a few hundred were tested annually.

Which downers might have mad cow disease is also in dispute.

DeHaven said inspectors tested animals that were twitching, aggressive, nervous, stumbling or showing other signs of brain damage; they also test some dead or unconscious animals, which are not supposed to be sold for food.

The beef industry argues that many animals that are falling down are merely lame. Its critics claim that some downed animals are passed because they are just conscious enough to respond to a kick.

Tests in Japan have found the brain-wasting disease in apparently healthy animals.

Dr. Stanley Prusiner, a UCSF neurologist who discovered the proteins that cause mad cow disease, said he had warned Agriculture Secretary Ann Veneman recently that it was "just a matter of time" before the disease would be found in the United States.

He said he had told her the United States should immediately start testing every cow that showed signs of illness and eventually every single cow upon slaughter.

Prusiner, a Nobel laureate, said fast, accurate and inexpensive tests are available, including one that he has patented through his university that he says could add 2 or 3 cents a pound to the cost of beef.

The scientist said Veneman was getting poor advice from USDA scientists and had not seemed to share his sense of urgency when he met with her six weeks ago, after several months of seeking a meeting.

"We have met with many experts in this area, including Dr. Prusiner," said Veneman spokeswoman Julie Quick. "We welcome as much scientific input and insight as we can get on this very important issue. We want to make sure that our actions are based on the best available science."

On Thursday the Agriculture Department said it had received confirmation of its own tests from the Veterinary Laboratories Agency in Waybridge, England, that a Holstein cow that was slaughtered on Dec. 9 had the degenerative brain ailment bovine spongiform encephalopathy, or mad cow disease. More testing is planned.

An official close to the investigation said the cow came from Sunny Dene Ranch in Mabton, Wash., which has about 4,000 dairy cows.

Although neither DeHaven nor Engeljohn would say exactly what changes were contemplated, some food safety experts want a ban on eating any brain or nerve tissue, or on eating older animals, which are more likely to harbor mad cow. Others have suggested testing millions of animals and creating a national ear-tagging system that would track each animal from birth to slaughter. Others want to stop feeding herbivores any animal protein, which transmits the disease.

In some European countries, diseased carcasses are boiled down, dried into powder and then incinerated.

Engeljohn did say the department might take measures like those Canada adopted after it found a mad cow case in May.

But other than slaughtering and testing the herds in Alberta that the animal came from, Canada did not take aggressive measures compared with those used in Europe and Japan.

It has tested only about 10,000 animals in the last decade and has had a serious backlog of cases. Its one diseased cow was slaughtered in January and probably made into pet food. It was marked for testing because it was thin; pneumonia, not brain disease, was suspected. It was not tested until May.

"Compared to our neighbor to the north, we did pretty well," said John Maas, a professor of veterinary medicine at UC Davis.